Though the Sun is a constant in our lives, it is not tranquil. From deep within
our star, titanic energies rise to cause the surface to violently erupt. Hot tubes of plasma (called
magnetic loops) arc thousands of miles above the Sun, following invisible lines of magnetic force.

The travel time for the solar wind from the Sun to the Earth is two to four days.

Solar Explosions Blast Into Space

The Sun's corona can rip open and spew as much as 20 billion tons
of material into space -- equivalent to the mass of 200,000 cruise ships. These explosions are
known as coronal mass ejections (CMEs), the hurricanes of space weather.

When a CME ploughs into the solar wind, it can create a shock wave that accelerates particles
to dangerously high energies. Behind that shock wave, the CME expands into a huge cloud that
engulfs planets in its path with plasma.

Luckily for us, few CMEs are aimed at the Earth. If a CME erupts on the side of the Sun facing
us, the results around Earth can be spectacular and sometimes hazardous.

Sunspots are relatively dark patches on the Sun's bright surface. These regions of concentrated
magnetic fields can last from several hours to several months. They appear as dark spots because
they're cooler (4000 C) than the Sun's surrounding surface (6000 C). Sunspots tend to develop
in groups, with some individual spots covering areas 20 times the diameter of Earth.